Plastic materials have excellent electrical properties, but their surfaces tend to be electrically charged. Once electrically charged, the plastic materials can hardly leak electrical charge from their surfaces, often causing troubles at a forming step, working step or other various steps carried out until they are supplied to users as finished products.
Antistatic agents serve to cause an electrical charge to rapidly leak from the surface of plastic materials, avoiding various troubles. To this end, the plastic materials are kneaded or coated with low-molecular weight surface active agents as disclosed in "9586 Chemical Merchandise", Kagaku Kogyo Nipposha, pp. 775-776, or electrically-conductive resins, depending on usage.
The constituents of the photographic light-sensitive material are an electrically insulating support and photographic layers which often suffer from the accumulation of static charge caused by contact friction with or peeling off the surface of the same or a different kind of substance during the preparation or use of the photographic light-sensitive material. Static charge thus accumulated causes many troubles. The most serious trouble is a spot or branched feather-shaped linear mark produced by development of a photographic film which has been exposed to light on its light-sensitive emulsion layer by the discharge of accumulated static charge before development. This mark is a so-called static mark that can remarkably impair and occasionally destroy the commercial value of the photographic film. This phenomenon can be recognized only when the photographic light-sensitive material is developed and thus is a very difficult problem.
Static charge thus accumulated also causes secondary troubles. That is, static charge thus accumulated causes the photographic film to attract dust before or after processing or disables the photographic film to be uniformly coated. This is also a difficult problem.
Static marks developed on photographic light-sensitive materials by the accumulation of static charge become more remarkable as the sensitivity and processing rate of photographic light-sensitive materials increase. In particular, as photographic light-sensitive materials have recently been highly sensitized and often subjected to severe treatments such as high speed coating, high speed picture taking and high speed automatic development, they have become more susceptible to static marking. Further, as processed photographic light-sensitive materials have recently been more often treated, dust attraction can cause a serious trouble.
In order to eliminate the troubles caused by static charge, the above mentioned antistatic agents are preferably incorporated in the photographic light-sensitive material. However, antistatic agents commonly used in other fields cannot necessarily be used for photographic light-sensitive materials. Various restrictions peculiar to photographic light-sensitive materials are imposed on these antistatic agents. In other words, antistatic agents which can be used for photographic light-sensitive materials are required to exhibit excellent antistatic properties as well as to meet other requirements; that is, they must have no adverse effects on photographic properties such as sensitivity, fog, graininess and sharpness of photographic light-sensitive materials, the film strength of photographic light-sensitive materials and the resistance of photographic light-sensitive materials to adhesion, they must not accelerate the fatigue of the processing solution for photographic light-sensitive materials, they must not contaminate the conveying roller, and they must not lower the adhesive strength between the constituent layers of photographic light-sensitive materials. Thus, antistatic agents which can be used for photographic light-sensitive materials have many restrictions.
Examples of antistatic agents which have heretofore been used for photographic light-sensitive materials include ionic electrically-conductive substances, hygroscopic substances, and inorganic electrically-conductive grains. Most of these anti-static agents serve to render the light-sensitive materials electrically conductive so that the electrical charge can be rapidly leaked before the discharge of accumulated static charge.
As an approach for directly rendering the support for photographic light-sensitive materials anti-static, a method which comprises directly blending such a substance in a high molecular weight compound to be used as a support and a method which comprises coating such a substance on the surface of a support have been known. In the latter case, an antistatic agent may be coated singly or in combination with a high-molecular weight compound such as gelatin, polyvinyl alcohol, cellulose acetate, polyvinyl formal and polyvinyl butyral. Alternatively, an antistatic agent may be incorporated in a light-sensitive emulsion layer to be provided on a support or light-insensitive auxiliary layers (e.g., back layer, antihalation layer, interlayer, protective layer). Further, an antistatic agent may be coated on developed light-sensitive materials to inhibit the attraction of dust during the treatment of the developed light-sensitive materials.
Among these antistatic agents, cationic polymer compounds are particularly important for the antistatic properties. A typical example of such cationic polymer compounds include so-called ionen type polymers containing a dissociative group in their main chain as disclosed in JP-A-48-91165, JP-A-54-18728, JP-A-54-159222, JP-A-64-13542, JP-A-64-28633, JP-A-64-28634, JP-A-64-29839, JP-A-64-29840, JP-A-64-88449, JP-A-2-116843, JP-A-1-245252, and JP-A-1-245253 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), and U.S. Pat. No. 4,898,808.
Although the above mentioned ionen type polymers exhibit excellent antistatic properties, they are disadvantageous in that they are eluted with a developer to form a complex with an anionic compound eluted from an emulsion layer, causing turbidity or contamination in the developer.
As antistatic agents which eliminate these difficulties, crosslinked grains of cationic polymer as disclosed in JP-A-53-45231, JP-B-60-51693 (the term "JP-B" as used herein means an "examined Japanese patent publication"), and U.S. Pat. No. 4,070,189 have been described. In general, the coating of an antistatic agent is often effected in an organic solvent system to lighten the drying load. Since the above-mentioned crosslinked grains cannot be synthesized in one stage in an organic solvent system, a step is required which comprises emulsion polymerization followed by a quaternarizing reaction and a changing of the medium from water to an organic solvent system. The addition of this step naturally worsens the productivity of the above-mentioned crosslinked grains.